Numerous pre-clinical studies suggest that surface localization of u-PA is critical to its putative role in promoting tumor invasiveness. The goal of this proposal is to characterize the role of cell surface- associated u-PA in the growth, angiogenesis, and metastasis of prostate cancer. The effects of inhibiting this reaction on the progression of prostate cancer will be assessed with the ultimate aim of designing drugs that might inhibit the progression of prostate cancer. First, the extent to which expression of the urokinase receptor (u-PAR) by human prostate cancer cell lines is involved in tumor growth and metastasis in nude mice following orthotopic implantation will be determined. Three approaches will be used to inhibit the interaction between u-PA and its receptor: 1) expression in tumor cells of mutant u-PA molecules which are proteolytically-inactive but retain the ability to occupy the u-PAR, 2) expression of soluble forms of the u-PAR in the cancer cells as a competitive inhibitor and, 3) infusion of anti-u-PAR antibodies. Metastasis will be identified and quantified using expression of recombinant chloramphenicol acetyl transferase (CAT) by tumor cells. This technique permits a highly sensitive and quantitative measurement for tumor cell metastasis to lymph nodes, liver, lungs, and brain by assaying organ homogeneity for CAT activity. The role of the u-PA system in the host angiogenic response will be evaluated by over- expressing an inactive murine u-PA in the tumor cells and determining the effect of inhibiting the u-PAR on the developing tumor microvasculature. A second aim is to obtain structural information relating to the interaction of u-PA with its receptor in order to provide a basis for the development of therapeutic agents. Soluble forms of u-PAR protein will be expressed. Those that retain u-PA binding activity will be examined by X-ray crystallography and solution phase NMR. The third main goal of this project will be to determine the role of cell-surface activation of plasminogen in morphogenesis of prostatic ducts during development. Using inhibitors of the u-PAR, the importance of the receptor in ductal branching in the prostate in an organ culture system. In addition, expression of u-PA and u-PAR will be examined in murine prostates obtained at birth and various times early in the post- natal period and correlated with ductal branching. These experiments will define specific aspects of branching ductal morphogenesis that require cell surface u-PA.